The liquor produced by anaerobic digestion is suitable for use as a fertiliser but in many situations including emergency aid there is no land which is available for the growing of crops. There is therefore a need to find a way to dispose of the digested sludge material at the lowest cost and with minimal risk to humans and the environment.

Current practice today

Most sewage in aid and development situations is not treated. Where it is treated, the disposal is usually by overflow into nearby water courses. Alternatively it is fed into large lagoons and allowed to evaporate.

Ambitions for a better solution

SOWTech have sought to design and develop a way to reduce the bulk of the material, which is predominantly water, and to try and capture for possible reuse, the beneficial components of the sludge material.

The "SOWTech Design"

Water from waste treatment plants can be rich in nutrients and where possible should be used to fertilise and irrigate crops. However such land is not always available and the waste water has to be disposed of rather then reused.

If this is left in large lagoons it can attract flies and vermin, it can be odorous and can crust over preventing the water evaporating. SOWTech have designed Soil Donuts that can capture the particles in the waste water and give an increased surface area for enhanced evaporation of the water content. The Soil Donut can be reused many time and when it does need emptying the soil can be used for growing crops.